@article{Monks2002,
  author    = {{Monks, Kenneth G.}},
  title     = {{$3X+1$ Minus the $+$}},
  journal   = {{Discrete Math. Theor. Comput. Sci.}},
  year      = {{2002}},
  volume    = {{5}},
  pages     = {{47--53}},
  note      = {{MR 2203f:11030}},
}